Yarn is a package manager for your code. It allows you to use and share (e.g. JavaScript) code with other developers from around the world. Yarn does this quickly, securely, and reliably so you don’t ever have to worry.
Yarn allows you to use other developers’ solutions to different problems, making it easier for you to develop your software. If you have problems, you can report issues or contribute back, and when the problem is fixed, you can use Yarn to keep it all up to date.
Code is shared through something called a package (sometimes referred to as a module). A package contains all the code being shared as well as a package.json file which describes the package.
Install via npm
It is recommended to install Yarn through the npm package manager, which comes bundled with Node.js when you install it on your system.
Once you have npm installed you can run the following both to install and upgrade Yarn:
(npm install --global yarn)
Check that Yarn is installed by running:
(yarn --version)
yarn install
yarn start
Runs the app in the development mode.
Open http://localhost:3000 to view it in the browser.
yarn test
Launches the test runner in the interactive watch mode.
See the section about running tests for more information.
yarn build
Builds the app for production to the build folder.